Saliva is essential for preservation of oral health. It aids in preparation of the initial food bolus, assist in taste and swallowing, and lubricates the oral mucosa. In addition it has antiviral, antifungal, and antibacterial properties. Consequently, salivary gland dysfunction can lead to complaints of oral dryness (xerostomia). Diseases of the thyroid gland, hyperthyroidism and hypothyroidism, and their treatment have also been suggested to cause salivary gland dysfunction. In addition head and neck radiation therapy, treatment for head and neck cancers can cause irreversible salivary gland function. This case study, reported one patient with thyroid cancer in which the thyroid gland has been removed and received head and neck radiation therapy.